package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

/**
 * 缓存工具类 封装了 StringRedisTemplate
 */
@Slf4j
@Component
public class CacheClient  {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
//    将对象序列化后存入缓存并设置TTL
    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }
//    加上逻辑过期字段存入缓存 解决缓存击穿
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }
//    取数据 dbFallback是缓存未命中后数据库的查询函数
    public <R,ID> R queryWithPassThrough(String keyPrefix,ID id, Class<R> type, Function<ID,R> dbFallback,Long time,TimeUnit unit){
        String key = keyPrefix+id;
        String json = stringRedisTemplate.opsForValue().get(key);
        if(StrUtil.isNotBlank(json)){
            return JSONUtil.toBean(json,type);
        }
        if(json!=null){
            return null;
        }
        R r = dbFallback.apply(id);
        if(r == null){
            stringRedisTemplate.opsForValue().set(key,"",time,unit);
            return null;
        }
        this.set(key,r,time,unit);
        return r;
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <R,ID> R queryWithLogicalExpire(String keyPrefix, String lockKeyPrefix,ID id,Class<R> type,Function<ID,R>dbFallback,Long time,TimeUnit unit){
        //        1.从redis中查缓存
        String key = keyPrefix +id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);
//        2.若不存在于缓存
        if(StrUtil.isBlank(shopJson)) {
            return null;
        }
//       3.若存在 判断是否过期
        RedisData redisData = JSONUtil.toBean(shopJson,RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();
        if(expireTime.isAfter(LocalDateTime.now())){
//            未过期 直接返回店铺信息
            return r;
        }
//        已过期 需要缓存重建
        String lockKey = lockKeyPrefix+id;
        boolean isLock = tryLock(lockKey);
        if(isLock){
//            获取到锁 另起线程重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    R r1 = dbFallback.apply(id);
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    unlock(lockKey);
                }
            });

        }

        return r;
    }

    /**
     * 互斥锁上锁
     * @param key
     * @return
     */
    private boolean tryLock(String key){
//        若键值对已存在 返回false
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key,"1",10,TimeUnit.SECONDS);
//        直接返回flag会拆箱 可能会返回空值
        return BooleanUtil.isTrue(flag);
    }

    /**
     * 互斥锁解锁
     * @param key
     */
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

}
